Parallel connected concentric conductor



y 1954 B. N. BOWERS PARALLEL CONNECTED CONCENTRIC CONDUCTOR Filed July19, 1949 III. "III.

am r .n e x as @N Wm 1 m mm B a relatively small portion Patented July27, 1954 PARALLEL CONNECTED CON CEN TRIC CONDUCTOR Benjamin N. Bowers,Pittsfield, Mass., assignor to General Electric Company, a corporationof New York Application July 19, 1949, Serial No. 105,546

8 Claims.

My invention relates to electrical conductor structures and, moreparticularly, to electrical conductor structures which are adapted tocarry relatively large 60 cycle alternating currents and alternatingcurrents of frequencies higher than 60 cycles.

When an alternating current is caused to flow in a conductor, certainmagnetic forces are set up within the conductor which give rise to aphenomenon which is commonly recognized and designated skin effect,whereby a relatively larger portion of the current is forced to ilow inthe radially outermost portions of the conductor and the innermostportions of the conductor carry of the current. This skin effect becomesmore pronounced as the current increases, as the diameter of theconductor increases, and also as the frequency of the alternatingcurrent conducted increases. As a result, it has been common practicewhere a conductor of large cross-section is required to make theconductor in the form of a hollow tube since, if a solid conductor wereused, the center portion would carry such a small part of the currentthat the additional cost and weight of the copper or other conductivematerial in this center portion is unjustified. This hollow conductorconstruction, however, results in a considerable Waste of space in thecenter of the conductor.

It is, therefore, an object of my invention to overcome skin effect andthereby to make use of the otherwise wasted space or wasted conductivematerial through the center of a conductor of large cross-sectionalarea.

This invention, in its broader aspects, consists essentially in thecombination of two or more series connected conductor sections, eachsection including two or more concentric conducting members. The membersof smaller diameter in one section are interconnected with members oflarger diameter in other sections to provide a number of parallelconductive paths, each path including conductors of various diameter andinsulated from the other paths except at the terminal ends of thecomplete conductor, so that the total current being conducted is dividedequally among the various parallel paths and all of the conductors ineach section carry approximately equal currents.

For additional objects and advantages, and for a better understanding ofthe invention, attention is now directed to the following descriptionand accompanying drawing, and also to the appended claims in which thefeatures of the in- 2 vention believed to be novel are particularlypointed out.

In the drawing, Fig. 1 is a view, partially in section, of oneembodiment of my invention; Fig. 2 is a similar view of a secondembodiment of my invention; and Fig. 3 is a view, partially in section,of my invention as incorporated into an induction apparatus such as atransformer.

In Fig. 1, conductor I consists of conductor sections 2 and 3, each ofwhich employs an inner conductin element 4 and an outer conductingelement 5. Elements 4 and 5 are insulated from one another by a suitableinsulating material 6. The inner conductor 4 in section 2 is connectedto the outer conductor of section 3 by a suitable connector 7, and theinner conductor of section 3 is connected to the outer conductor ofsection 2 by a suitable connector 8. At the terminal ends of thesections 2 and 3 remote from the junction formed by the connectors l and3, the inner conductor 4 and outer conductor 5 are connected togetherthrough suitable terminals 9 and H3. Thus, between the terminals 9 and Ia there are two parallel paths through which the electrical current maybe conducted; one path from terminal 9 through inner conductor 4 ofsection 2, connector 1, outer conductor 5 of section 3 to terminal I 0,and the other parallel path from terminal 9 through outer conductor 5 ofsection 2, connector 8 and inner conductor 4 of section 3 to terminalIn. These two parallel paths are electrically equivalent and both paths,therefore, carry equal amounts of the current, since each path includesone section of inner conductor and one section of outer conductor.Therefore, the inner conductor elements and outer conductor ele-- mentsshare the current equally and skin efiect is thereby avoided.

Fig. 2 illustrates another embodiment of my invention, the conductorillustrated employing three concentric conductor elements and threeconductor sections to obtain more complete advantage of the principle ofmy invention where, for instance, a conductor of extremely largecrosssectional area is needed. An additional outer conductor element IIis added to each section and a complete section 23 is added.Interconnections I 2, l3, and I4 between conductor elements of differentdiameters in successive secin three parallel conductive paths. eachincluding one conductor element of each diameter so that each of thethree paths is the electrical equivalent of the other two and each,therefore, carries an equal share of the total current. It will beunderstood that the principle of my invention may be further extended bythe addition of conductor elements and conductor sections beyond the twoor three shown here.

In Fig. 3, the conductor of my invention is shown combined with atransformer employing parallel connected transformer coils. Here, myconductor sections 2" and 3" constitute insulating bushings which areemployed .as insulated lead-in conductors and the transformer coils l5and it themselves perform the function of interconnections between theinner conductor elements 4 in one section and the outer conductorelement in the other section. Although only two parallel connected coilsand .two conductor elements per section are employed here, the number ofcoils and elements could be increased to three or more.

In their ofiice as lead in conductors in Fig. 3, conductor sections 2and 3 are surrounded and supported by tubular insulating members i! andL8 which .are, in turn, supported upon the transformer casing 19 wherethey are retained in place (by metal supports :29. Outer conductorelement .5 and insulator tubes l1 and :8 are maintained in assembled,though spaced, relationship by conducting or insulated flange nuts 21which may be threaded over the lower portions of elements 5. Theinsulator 6 in an embodiment such as shown in Fig. 3, may consistentirely of air, but in other embodiments this insulator may be of anysuitable insulating material such as, for example, a resilientplastic.

While certain specific embodiments have been shown and described, itwill, of course, .be understood that various modifications may be madewithout departing from the invention. The appended claims are,therefore, intended to cover any such modifications within the truespirit and scope of the invention.

What I claim as new .and desire to secure by LettersPatent of the UnitedStates is:

1. A pair of insulated lead-in conductor sections for making electricalconnection between the exterior and interior of a casing, said conductor sections extending through a wall of said casing and eachcomprising an .inner conducting element and an outer conducting elementWith said outer element being insulated from and surrounding said innerelement over substantially all of the respective lengths of saidelements, the

ends of said elements in each lead-in conductor section exteriorly .ofsaid casing being directly interconnected, and .at the ends of saidconductor sections positioned interiorly of said casing, the interiorconducting element for one section being conductively connected to theouter conducting element of the other section and the outer .conductingelement of the said onesection being conductively connected to theinterior conducting element of thesaid-other section, one pair'ofconductive'ly connected elements being insulated from the other ,pair of.conductively connected elements within said casing.

2. An electrical conductor comprising a plurality of sectionsinterconnected at their ends, each section including ,a plurality ofconducting elements of different outer .dimensions including aninnermost conducting element and outer hollow elements of progressivelyincreasingsize, each such element surrounding and being insulated fromthe next smaller element .over substantially all of the respectivelengths of said elements, interconnections at the ends of adjacentsections from individual elements in one section to individual elementsin the othersection, each of said interconnections connecting an elementof one size in one section to an element of a difierent size in theadjacent section, the ends of the conducting elements at the terminalends of the terminal sections of said electrical conductor beingdirectly interconnected so that said electrical conductor comprises anumber -:of parallel con ductive paths equal to the number of elementsin each section.

3. An electrical current conductive apparatus including two pairs ofconcentric electrical conductor elements, each pair comprising an innerconductor element and a hollow outer conductor element, .said innerconductor element and said outer conductor element in each pair beinginsulated from each other over substantially all of the respectivelengths of said elements, the two elements in each pair being directlyconnected together at one end and the other end of the inner element ofeach pair being connected respectively to the other end of the outerelement cf the other pair.

4. An electrical current conductive apparatus including -a plurality ofconductor sections interconnected at their ends, each section includinga plurality of conducting elements of different outer dimensionsincluding an innermost conducting element and outer hollow elements ofprogressively increasing size, each such element surrounding and beinginsulated from the next smaller element over substantially all of therespective lengths of said elements, interconnections at the ends ofadjacent sections from individual elements in one section to individualelements in the other section, each of said interconnections connectingan element of onesize in one section to an element of a different sizein the adjacent section, the ends of the conducting elements at theterminal ends L01 the terminal sections of said electrical conductorbeing directly interconnected so that said electrical apparatus includesa number of parallel conductive paths equal to the number of elements ineach section, each of said paths including the same number of elementsof each size.

.5. An electrical conductor comprising a plurality of sectionsinterconnected at their ends, each section including a plurality ofcoaxial cylindrical conducting elements .of different outer diametersincluding .an innermost element and outer hollow cylindrical elements ofprogressively increasing diameter, each such element surrounding .andbeing insulated from the next smaller element over substantially .all ofthe respective lengths of said elements, interconnections at the ends.of adjacent sections from individual ele ments in one section toindividual elements in the other section, each of said interconnectionsconnecting an element of one size in one section to an element-of a.diilerentsize in the adjacent section, the ends of the conductingelements at the terminal .ends of the terminal sections .of saidelectrical conductor being directly interconnected so that saidelectrical conductor comprises a number of parallel conductive pathsequal .to the number of elements in each section, each of said pathsincluding the same number of elements of each size.

6. A pair of insulated lead-in conductor sections for making electricalconnection between the exteriorand interior or" a casing, said conductorsections extending-through a wall of saidcasing and each comprising atleast one inner conducting element and at least one outer conductingelement, with the respective conducting elements in each section beinginsulated from each other and coaxially positioned with respect to eachother, the ends of said elements in each lead-in conductor sectionexteriorly of said casing being directly conductively interconnected,and at the ends of said conductor sections positioned interiorly of saidcasing the conducting elements of one section being conductivelyconnected to the conducting elements of the other section in such mannerthat a conducting element of a given diameter in one section is alwaysconnected to a conducting element of a diiferent diameter in the othersection.

7. A pair of insulating bushings for making electrical connectionbetween the exterior and interior of an enclosing casing, each of saidbushings having an outer insulating shell and an outer and an innerconducting element coaxially disposed radially inwardly of saidinsulating shell, the outer conducting element of each of said bushingsbeing insulated from and surrounding the inner conducting element ofsaid bushing, the ends of said elements for each of said bushings whichare disposed exteriorly of said casing being directly conductivelyinterconnected, and at the ends of said respective bushings extendinginteriorly of said casing the inner conducting element of each bushingbeing conductively connected to the outer conducting element of theother bushing and the outer conducting element of each bushing beingconductively connected to the inner conducting element of the otherbushing.

8. A pair of insulating bushings for making electrical connectionbetween'the exterior and interior of an enclosing casing,;said bushingsextending through a wall of said casing and each comprising an outerinsulating shell and at least one inner conducting elementand at leastone outer conducting element disposed radially inwardly of saidinsulating shell; with the respective conducting elements in eachbushing being insulated from each other, the conducting elements in eachbushing being coaxially positioned with respect to each other, the endsof said conducting elements in each bushing positioned exteriorly ofsaid enclosing casing being directly conductively interconnected, and atthe ends of said bushings positioned interiorly of said casing theconducting elements of one section being conductively connected to theconducting elements of the other section in such manner that aconducting element of a given diameter in one section is alwaysconnected to a conducting element of a different diameter in the othersection.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,096,175 Kitsee May 12, 1914 2,115,761 Blumlein May 3, 19382,130,309 Nergaard Sept. 13, 1938 2,526,942 Fuchs Oct. 24, 1950 FOREIGNPATENTS Number Country Date 110,576 Switzerland June 16, 1925 272,407Great Britain June 16, 1927

